Emergency breathing equipment gives victims of accidents and disasters a personal supply of breathing air to allow them to escape to safety. It may also be utilized by rescue personnel attempting to reach and assist such victims. Such equipment may be utilized in circumstances requiring escape from a submerged vehicle or where breathing air is contaminated by smoke from combustion or release of a dangerous gas. Such apparatus may be placed, for example, aboard aircraft making long over water passages and in small remote work areas where there is a present danger of fire or release of a dangerous gas.
Emergency breathing equipment of the prior art has generally included large, cumbersome gas bottles in which air is stored at moderate pressures of the order of 2,000 psi. In these devices, air is released from the bottle by activation of a valve. Thus, the bottles of such devices are not sealed and, as the valves may leak, the bottles must be checked from time to time, before each flight in the case of equipment utilized aboard aircraft, to assure adequate air pressure for proper operation.
Recently, emergency breathing devices utilizing small sealed air canisters storing air at higher pressures than previous equipment, of the order of 4,000 to 4,500 psi have been suggested. To be acceptable and effective, these devices require a firing mechanism which is compact, reliable and reusable and which provides for adjustment of the threshold force required to initiate breaking of the air canister seal and for lock-up of the firing mechanism to prevent unintentional breaking of the seal.